The present invention relates generally to hydraulically-actuated system, and more particularly to a electrically driven actuator of a variable delivery fixed displacement pump.
U.S. Pat. No. 6,035,828 to Anderson et al. describes a variable delivery actuating fluid pump for a hydraulically-actuated fuel injection system. In this system, a high pressure rail supplies pressurized lubricating oil to a plurality of hydraulically-actuated fuel injectors mounted in a diesel engine. The high pressure rail is pressurized by a variable delivery fixed displacement type pump that is driven directly by the engine. Pump pressure control is provided by hydraulically varying the high pressure output of the pump. This is accomplished by providing a piston arrangement in the pump that incorporates a moveable sleeve on the outside of the pistons. Depending upon the position of the sleeve, a spill port on the piston can be opened or closed. When the spill port is opened, the fluid is spilled back into the low pressure side of the pump, instead of being pushed into the high pressure rail. The position of the sleeve is maintained by a hydraulic actuator. Fluid in the actuator moves an actuator shaft, which in turn moves the sleeve.
While the Anderson et al. hydraulically-actuated system using a variable delivery pump performs better than previous systems, there remains room for improvement. The complicated mechanical structure of the pump and hydraulic actuator provides potential leak paths for hydraulic fluid. Also, because the viscosity of lubricating oil varies due to temperature, control of the pump may be sluggish when the oil is of an extremely cold temperature.
The present invention is directed to overcoming problems associated with, and improving upon, hydraulically-actuated systems of the prior art.
In a first aspect of the invention, a fixed displacement variable delivery pump is provided. The pump includes a housing, a plurality of pistons and a control device. A linear motion device that is moveable in responses to electrical energy is provided. A linkage connects the linear motion device to a plurality of sleeves on the pistons. Movement of the linear motion device in turn moves the sleeves and varies the output of the pump.
In another aspect of the invention an electrically driven linear motion device for a fixed displacement variable delivery pump is provided. The linear motion device includes a body, a piston slidably disposed in the body, a sleeve disposed about the piston, a field coil, an armature and a linkage moving the sleeve relative to said piston in response to movement of the armature.
In yet another aspect of the invention a fluid delivery system is provided. The fluid delivery system includes a fixed displacement variable delivery pump having a piston, a sleeve disposed about the piston and a high pressure outlet. An electrically driven linear motion device is connected to the sleeve and moves the sleeve relative to the piston. A high pressure rail is connected the high pressure outlet and a pressure sensor, for delivering a pressure signal is connected to the high pressure rail. An electronic control module is connected to the linear motion device and delivers a drive signal in response to a reviewing the pressure signal.